Image display apparatuses employing reflective spatial light modulators have been proposed. FIG. 1 provides a plan view of the configuration of a conventional image display apparatus. In the image display apparatus shown in FIG. 1 light beams emitted from a white light source 101 are formed into parallel light beams by a concave reflector 102 before entering a polarized light selector 103.
This polarized light selector 103 consisting of a polarizing plate or ps-converter forms light beams emitted from the white light source 101 into linearly polarized light and passes that light. Red, green and blue light of a light beam emitted from the white light source 101 each become linearly polarized light of the same plane of polarization with respect to each other.
Light beams emitted from the white light source 101 enter a primary multilayered phase differentiation filter 104. This multilayered phase differentiation filter 104, providing optical elements comprising a multilayered arrangement of phase plates, rotates the inclination of the plane of polarization of specific wavelength regions only by 90°. The plane of polarization of green and blue light in light beams passing this primary multilayered phase differentiation filter 104 is perpendicular in relation to the plane of polarization of red light.
A light beam passed from this primary multilayered phase differentiation filter 104 then enters a primary polarized light beam splitter 105. In relation to a reflective surface 105a in this primary polarized light beam splitter 105, red light becomes s-polarized light and green and blue light become p-polarized light. Thus, in this primary polarized light beam splitter 105 red light is reflected at the reflective surface 105a while the green and blue light pass the reflective surface 105a. 
Green and blue light emitted from the primary polarized light beam splitter 105 enters a secondary multilayered phase differentiation filter 109. In this secondary multilayered phase differentiation filter 109 the plane of polarization of green light is made into a condition perpendicular to the plane of polarization of blue light, and this green and blue light pass the secondary multilayered phase differentiation filter 109.
Green and blue light directed from the secondary multilayered phase differentiation filter 109 enters a secondary polarized light beam splitter 106. In relation to a reflective surface 106a in this secondary polarized light beam splitter 106, green light becomes s-polarized light and blue light becomes p-polarized light.
The green light is reflected at this reflective surface 106a, and is directed out from the secondary polarized light beam splitter 106 entering a reflective spatial light modulator for green light 112. Light entering this reflective spatial light modulator for green light 112, a liquid crystal display device, undergoes polarization-modulation coordinated to the green light component of a displayed image and is reflected.
Primary modulated light modulated and reflected by the reflective spatial light modulator for green light 112 reenters the secondary polarized light beam splitter 106. As this primary modulated light becomes p-polarized light in relation to the reflective surface 106a the primary modulated light passes the reflective surface 106a and is emitted from the secondary polarized light beam splitter 106 in a direction different to the direction of returning to the primary polarized light beam splitter 105.
Blue light passes the reflective surface 106a and is emitted from the secondary polarized light beam splitter 106 entering a reflective spatial light modulator for blue light 107. Light entering this reflective spatial light modulator for blue light 107, a liquid crystal display device, undergoes polarization-modulation coordinated to the blue light component of a displayed image and is reflected.
Secondary modulated light modulated and reflected by the reflective spatial light modulator for blue light 107 reenters the secondary polarized light beam splitter 106. As this secondary modulated light becomes s-polarized light in relation to the reflective surface 106a this light is reflected at the reflective surface 106a and emitted from the secondary polarized light beam splitter 106 in a direction different to the direction of returning to the primary polarized light beam splitter 105.
The primary and secondary modulated lights thus emitted from the secondary polarized light beam splitter 106 enter a tertiary multilayered phase differentiation filter 109. This tertiary multilayered phase differentiation filter 109 rotates the plane of polarization of the primary modulated light only by 90° and injects the primary and secondary modulated lights into a fourth polarized light beam splitter 116.
Red light emitted from the primary polarized light beam splitter 105 enters the tertiary polarized light beam splitter 110. In this tertiary polarized light beam splitter 110, red light becomes s-polarized light in relation to a reflective surface 110a. The red light is reflected at the reflective surface 110a and emitted from the tertiary polarized light beam splitter 110 entering a reflective spatial light modulator for red light 111.
Light entering this reflective spatial light modulator for red light 111, a liquid crystal display device, undergoes polarization-modulation coordinated to the red light component of a displayed image and is reflected.
Tertiary modulated light modulated and reflected at the reflective spatial light modulator for red light 111 reenters the tertiary polarized light beam splitter 110. As this tertiary modulated light becomes p-polarized light in relation to the reflective surface 110a this light passes the reflective surface 110a and is emitted from the tertiary polarized light beam splitter 110 and injected into the fourth polarized light beam splitter 116.
In this fourth polarized light beam splitter 116, the primary modulated and secondary modulated lights becomes s-polarized light in relation to the reflective surface 116a and are reflected at the reflective surface 116a and emitted from the fourth polarized light beam splitter 116. The tertiary modulated light passes through the reflective surface 116a and is directed out from the fourth polarized light beam splitter 116. The primary, secondary and tertiary modulated lights are synthesized in this way.
Light directed out from the fourth polarized light beam splitter 116 enters an optical projection system 118. This optical projection system 118 projects the light thus input on to a screen not shown in the drawing, providing an image display thereof.
Japanese Patent Application Laid-Open Publication No. 2002-122810 and No. 2002-287094 are hereby cited as prior patent documents in connection with the present technical field.
Of light emitted from the fourth polarized light beam splitter 116 in a conventional image display apparatus as described above, the primary and secondary modulated lights enter the optical projection system 118 in a condition of s-polarized light in relation to the reflective surface 116a while the tertiary modulated light enters the optical projection system 118 in a condition of p-polarized light in relation to the reflective surface 116a. 
The optical projection system 118 is constructed of a plurality of lenses. An anti-reflection film is formed on this plurality of lenses to improve the rate of light permeation. Ideally, such an anti-reflection film would result in no reflection occurring, however a small degree of reflection in the order of a few percent does occur.
Accordingly, a part of a light beam entering the optical projection system 118 is reflected, the direction of light polarization thereof remaining unchanged, by the plurality of lenses of the optical projection system 118 and reenters the fourth polarized light beam splitter 116 in that condition.
In this way light reentering the fourth polarized light beam splitter 116 from the optical projection system 118 returns respectively in accordance with the color (i.e. blue, green or red) to the reflective spatial light modulators 107, 111 or 112. This returning light (R′, G′, B′) is again reflected and directed into the optical projection system 118.
Light thus reentering the optical projection system 118 is superimposed on the light corresponding to that of the original image information and projected on screen. The image thus displayed contains superimposition of unnecessary image elements resulting in substantial deterioration in image quality. That is to say, such an image has poor contrast and the ghosting phenomena occur.
With the foregoing in view the present invention provides an image display apparatus employing reflective spatial light modulators that displays a high-quality image, having unnecessary image elements removed and having good contrast and no occurrence of the ghosting phenomena.